- Carotid contrast-enhanced ultrasound (CEUS): For CEUS imaging intravenous continuous infusion (VueJectTM, Bracco, Milan, Italy) of 4.8ml of phospholipid-stabilized sulfur hexafluoride microspheres (SonoVueTM, Bracco) at a flow rate of 1ml/min preceded by a bolus inject of 1ml will be used. The examinations will be performed using a Philips (Bothel, WA) iU22 ultrasound scanner equipped with a linear array L9-3 MHz probe and with ultrasound contrast harmonic software (puls inversion / power modulation). Following setting for CEUS imaging will be implemented: mechanical index 0.06, overall gain 80%, compression 36 will be provided as "pre sets". Imaging after start of contrast injection will be performed during 2 minutes at the right side followed by 2 minutes at the left side and will be standardized as follows: using a longitudinal view focusing on the carotid stenosis at the carotid bulb, or the proximal part of the ICA. The standard and CEUS studies will be stored digitally as DICOM format for further analysis and quantification.